Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2017 USD ($) Plan	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 2,440	$ 2,440	$ 4,880	$ 4,880
Interest cost		4,927	5,315	9,855	10,630
Expected return on plan assets		(6,971)	(6,901)	(13,942)	(13,802)
Amortization of prior service cost (credit)		0	0	0	0
Amortization of net loss (gain)		3,245	2,997	6,490	5,994
Net periodic benefit cost (credit)		3,641	3,851	7,283	7,702
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation		574	638	722	716
Net benefit cost (credit) recognized for financial reporting		4,215	4,489	8,005	8,418
Total contributions to the pension plans during the period	$ 23,000
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		219	194	438	388
Interest cost		415	455	830	910
Expected return on plan assets		(589)	(594)	(1,178)	(1,188)
Amortization of prior service cost (credit)		(100)	(100)	(200)	(200)
Amortization of net loss (gain)		(155)	(146)	(310)	(292)
Net periodic benefit cost (credit)		(210)	(191)	(420)	(382)
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (210)	$ (191)	$ (420)	$ (382)
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Total contributions to the pension plans during the period	$ 150,000
Number of Xcel Energy's pension plans to which contributions were made | Plan	4